Inter-access network handover

1. In a wireless network environment comprising first and second packet-switched access networks, each access network using a tunnelling-type micro-mobility protocol and a Quality of Service (QoS) routing protocol to route packet data to and from mobile nodes attached thereto, and each access network comprising an access router to which a mobile node may attach, a mobility agent with which said mobile node may register and a gateway, a method of facilitating network layer handover of said mobile node from said first access network to said second access network, said mobile node registered in said first access network with a serving mobility agent, which method comprises the steps of: (a) said mobile node receiving a router advertisement from said second access network, which router advertisement comprises a network-layer address of a target mobility agent in said second access network with which said mobile node may register, (b) said mobile node forwarding said network-layer address to said serving mobility agent, said serving mobility agent may communicate with said target mobility agent to facilitate network-layer handover of said mobile node to said second access network; and (c) said mobile node transmitting an identifier with said router advertisement, which identifier is useable to identify said mobile node in both said first and second access networks; wherein following handover of said mobile node at the physical and link layers, said mobile node initiates a handover at the network layer by sending to said target mobility agent a registration message comprising said identifier of said mobile node; and wherein upon receipt of said registration message, said target mobility agent uses said identifier to look up a pre-computed QoS route(s) stored for said mobile node.

2. A method according to claim 1 , wherein step (b) comprises said mobile node forwarding said router advertisement substantially as received.

3. A method according to claim 1 , further comprising the steps of said mobile node configuring said identifier as an on-link care-of address (LCoA) using data within said router advertisement, and forwarding said on-link care-of address to said serving mobility agent with said router advertisement.

4. A method according to claim 1 , further comprising the step of said serving mobility agent storing and forwarding said identifier to said target mobility agent.

5. A method according to claim 1 , further comprising the step of said first access network using said network-layer address to send handover data about ongoing session(s) of said mobile node to said second access network, upon receipt of which said second access network uses said data to perform at least a part of its admission procedure prior to handover of said mobile node.

6. A method according to claim 5 , wherein said handover data comprises quality of service (QoS) context data useable by said target mobility agent to determine as part of said admission procedure whether or not said second access network is able to provide the same or a similar QoS to said ongoing session(s) of said mobile node.

7. A method according to claim 5 , further comprising the step of said target mobility agent initiating computation of at least one QoS route across said second access network for packet data of said ongoing session(s) of said mobile node.

8. A method according to claim 5 , wherein if said second access network has determined that it can meet the QoS requirements of said ongoing session(s), either at the requested level or some other level, the method further comprises the step of establishing a temporary tunnel between said serving mobility agent and said target mobility agent, which temporary tunnel is useable to route packets arriving at said serving mobility agent intended for said mobile node to said target mobility agent.

9. A method according to claim 8 , wherein following handover of said mobile node at the physical and link layers, said serving mobility agent forwards packets addressed to said mobile node through said temporary tunnel to said target access network.

10. A method according to claim 1 , further comprising the step of said target access router storing said identifier for subsequent identification of said mobile node.

11. A method according to claim 1 , wherein messages sent by said mobile node to said serving mobility agent and to said target mobility agent comprise a local binding update message of a type according to HMIPv6, which message comprises a flag indicate to said mobility agents whether the message is a normal local binding update, a local binding update with a router advertisement or a local binding update following handover preparation.

12. A packet-switched wireless access network using a tunnelling-type micro-mobility protocol and a Quality of Service (QoS) routing protocol to route packet data to and from mobile nodes attached thereto, and which comprises: an access router to which a mobile node may attach, a mobility agent with which said mobile node may register and a gateway, said mobile node registered in said packet-switched wireless access network with a serving mobility agent, said packet-switched wireless access network for facilitating network layer handover of said mobile node to another access network, and in which said serving mobility agent is configured to receive a network-layer address from said mobile node, which network layer address is of a target mobility agent in said other access network with which said mobile node may register, whereby said serving mobility agent may communicate with said target mobility agent using said network layer address to facilitate network-layer handover of said mobile node to said other access network; wherein said mobile node transmits an identifier, which identifier is useable to identify said mobile node in both said first and second access networks; wherein following handover of said mobile node to said other access network, said mobile node initiates a handover at the network layer by sending to said target mobility agent a registration message comprising said identifier of said mobile node; and wherein upon receipt of said registration message, said target mobility agent uses said identifier to look up a pre-computed QoS route(s) stored for said mobile node.

13. A packet-switched wireless access network using a tunnelling-type micro-mobility protocol and a Quality of Service (QoS) routing protocol to route packet data to and from mobile nodes attached thereto, and which comprises: an access router to which a mobile node may attach, a target mobility agent with which said mobile node may register and a gateway; wherein the packet-switched wireless access network is configured to receive handover data from another access network about an ongoing session(s) of said mobile node in said other access network, and upon receipt to use said handover data to perform at least a part of its admission procedure prior to handover of said mobile node from said other access network; the handover data further comprising network-layer address of a target mobility agent in said second access network; wherein said mobile node transmits an identifier, which identifier is useable to identify said mobile node in both of the packet-switched wireless access network and said other access network; wherein following handover of said mobile node to said other access network, said mobile node initiates a handover at the network layer by sending to said target mobility agent a registration message comprising said identifier of said mobile node; and wherein upon receipt of said registration message, said target mobility agent uses said identifier to look up a pre-computed QoS route(s) stored for said mobile node.

14. In a wireless network environment comprising first and second packet-switched access networks, each access network using a tunnelling-type micro-mobility protocol and a Quality of Service (QoS) routing protocol to route packet data to and from mobile nodes attached thereto, and each access network comprising an access router to which a mobile node may attach, a mobility agent with which said mobile node may register and a gateway, a method of facilitating network layer handover of said mobile node from said first access network to said second access network, said mobile node registered in said first access network with a serving mobility agent, which method comprises the steps of: (a) said mobile node receiving a router advertisement from said second access network, which router advertisement comprises a network-layer address of a target mobility agent in said second access network with which said mobile node may register; and (b) said mobile node transmitting an identifier with said router advertisement, which identifier is useable to identify said mobile node in both said first and second access networks (a) said mobile node forwarding said network-layer address to said serving mobility agent, whereby said serving mobility agent may communicate with said target mobility agent to facilitate network-layer handover of said mobile node to said second access network (d) said mobile node initiates a handover at the network layer by sending to said target mobility agent a registration message comprising said identifier of said mobile node; and (e) said target mobility agent uses said identifier to lookup a pre-computed QoS route(s) stored for said mobile node.